The inventors have observed that chemical vapor deposition of cobalt can be used as a metal deposition technique for applications such as forming metal interconnects in an integrated circuit. This may be accomplished, for example, by growing metal films directly onto a dielectric layer, or alternatively, onto a barrier layer, such as titanium nitride (TiN). For a logic-contact fill application, a sputter clean process may be performed to remove oxide from a bottom of an interface, followed by physical vapor deposition of a titanium layer prior to a low-resistivity metal fill. However, the inventors have observed that using such a process for a cobalt fill may undesirably result in the deposition of a cobalt film with a void trapped inside the feature.
Accordingly, the inventors have developed improved techniques to deposit cobalt in features disposed in a substrate.